The present invention relates to a blade guard arrangement in a motor driven chop saw, and more particularly to a lower blade guard arrangement in the chop saw which is pivotally mounted for movement between a raised rest position and a lowered operational position.
The chop saw generally provides an upper safety guard which partially encases a circular saw-blade, and a swingable lower blade guard which covers the exposed segment of the saw-blade when the saw is in the raised rest position. When the upper safety guard is pivotally moved to the lowered operational position about a pivot shaft, the swingable lower blade guard is rotated to expose the saw-blade segment so as to chop wood or metal member mounted on a saw table with the circular sawblade. Such arrangement is well known in the art.
Further, according to one of the conventional arrangement, in response to the pivotal movements of the upper safety guard together with the circular saw-blade, the lower guard is pivotted by way of an actuation lever. In the latter type of arrangement, the actuation lever has one end portion pivotably connected to a frame element through a slide hinge which includes a pivot bolt engaged with a slot, and has the other end pivotally connected to the lower guard. Further, a tension springs are disposed each between the frame element and the upper blade guard in order to bias the upper blade guard and the circular saw-blade toward upper rest position. Such an arrangement is disclosed in U.S. Pat. No. 4,581,966.
With the structure, it would be rather troublesome to pivot the lower guard for exposing the saw-blade when the saw unit is at the upper rest position, if maintenance or changing of the saw-blade is required. More specifically, it is necessary to axially move the pivot bolt so as to allow actuation lever to slide along the pivot bolt in order to raise the lower blade guard without moving the saw unit from its rest position.
Further, with the structure, it would be impossible to adjust angular position of the lower guard so as to control a covering range with respect to the blade segment when the saw unit is in the rest position. Therefore, if the saw unit is assembled with having dimensional errors of the mechanical segments, the exposed blade portion is not sufficiently covered with the lower guard at the rest position. In order to avoid this problem, high dimensional accuracy is required for the assembly, which however is costly and requires nervous assembling labour.